A typical data communications network operates in a connectionless mode whereby there is no negotiation between the transmitter/receiver and the network with regard to the type or quantity of traffic that is to be sent. The transmitter simply sends the traffic on the network, and relies on the network components to deliver that traffic to the receiver accurately. In these networks, the protocols used by the transmitters and receivers are designed to accommodate the delay and loss that can arise from congestion. These same protocols also adapt the traffic flow to some extent to help alleviate congestion.
The networks are typically made up of routing nodes (routers) joined by physical links. The main function of the routing nodes is to direct incoming packets to the appropriate outgoing links. Congestion in the routing nodes is usually caused by an amount of traffic directed to a physical link exceeding its capacity. Queues form in the routing nodes and, when the queue (buffer) overflows, packets are lost. These buffers can smooth out transient surges of traffic, but ultimately, packets are discarded. For the Transmission Control Protocol (TCP from the Internet TCP/IP protocol suite), the loss of packets is a stimulus to reduce the rate of transmission and help share the link bandwidth in a controlled way. Other protocols, such as UDP (Unacknowledged Datagram Protocol), do not adapt in this way, and an application using UDP to transfer information can continue to send traffic regardless of congestion on the links.
High volume traffic streams on the network accelerate congestion and, if they cannot adapt to alleviate that congestion, can seriously impact the performance for all other network users. Streaming video is an example of such high volume traffic. Video is becoming more and more prevalent and it is anticipated that the presence of video sources may cause severe problems for TCP users.
One solution to this problem is to replace the routed (connectionless) network by a connection-oriented network such as an ATM network that allows for traffic segregation and bandwidth allocation. Unfortunately, this solution is undesirable because of capital costs, retraining and the requirement for new network management procedures.
Another solution is provided by the fact that the Internet Engineering Task Force (IETF) is defining new protocols for bandwidth management and newer high-end routers will have the capability of implementing bandwidth management. However, this solution requires new hardware or software and is not yet widely available. Furthermore, many network providers will find that replacing existing equipment is too expensive.
The background information presented herein clearly shows that there exists a need in the industry to provide a method for simple management of bandwidth in a data communication network particularly well suited for reducing congestion caused by high volume traffic streams.